package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import jakarta.annotation.Resource;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;


import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;
@Component
public class CacheClient {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value,Long time,TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,
        Long time,TimeUnit unit){
        String key = keyPrefix + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在把json字符串转成对象返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if(json != null){
            //返回一个错误信息
            return null;
        }
        //4.不存在，根据id查数据库
        R r = dbFallback.apply(id);

        //5.不存在 返回错误
        if(r == null){
            //将空值写进redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        //6.存在，先把数据转成json字符串写入redis中，然后返回
        this.set(key,r,time,unit);
        return r;
    }

    //创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //使用逻辑过期
    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,
                                           Long time,TimeUnit unit){
        String key = CACHE_SHOP_KEY +id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //未命中
            return null;
        }
        //3命中，需要判断过期时间，把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        //JSONUtil同样支持JSONObject进行反序列化为对象
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //4.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期返回店铺信息
            return r;
        }

        //5.2已过期，需要缓存重建
        String lockKey = keyPrefix + id;
        //6.缓存重建

        //6.1获取互斥锁
        boolean isLock = tryLock(lockKey);
        //6.2判断锁是否获取成功
        if(isLock){
            //6.3成功，开启独立线程
            CACHE_REBUILD_EXECUTOR.submit(()->{
                //重建缓存
                try {
                    //查数据库
                    R r1 =dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unlock(lockKey);
                    //释放锁
                }
            });
        }
        //6.4失败返回过期信息
        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
